Ground Fault Current Calculator Formula
Understand the math behind the ground fault current calculator. Each variable explained with a worked example.
Formulas Used
Ground Fault Current
ground_fault_current = system_voltage / (ground_path_impedance + source_impedance)Fault Power
fault_power = pow(system_voltage, 2) / (ground_path_impedance + source_impedance)Touch Voltage (at fault)
touch_voltage = system_voltage * ground_path_impedance / (ground_path_impedance + source_impedance)Variables
| Variable | Description | Default |
|---|---|---|
system_voltage | System Voltage (Phase-to-Ground)(V) | 277 |
ground_path_impedance | Ground Path Impedance(Ω) | 0.5 |
source_impedance | Source Impedance(Ω) | 0.1 |
How It Works
Ground Fault Current Estimation
Ground fault current flows when a live conductor contacts grounded metal. Its magnitude determines how quickly protection devices clear the fault.
Formula
I_gf = V_phase / (Z_ground + Z_source)
Touch Voltage = V_phase x Z_ground / (Z_ground + Z_source)
Low ground-path impedance ensures high fault current, which trips protective devices quickly. High impedance (poor grounding) results in low fault current that may not trip the breaker, leaving a dangerous condition.
Worked Example
277 V phase-to-ground, 0.5 ohm ground path, 0.1 ohm source impedance.
system_voltage = 277ground_path_impedance = 0.5source_impedance = 0.1
- 01Ground fault current: 277 / (0.5 + 0.1) = 461.7 A
- 02Fault power: 277^2 / 0.6 = 127,882 W
- 03Touch voltage: 277 x 0.5 / 0.6 = 230.8 V (dangerous)
Ready to run the numbers?
Open Ground Fault Current Calculator